Wednesday, June 15, 2011

When Will Tsunami Debris Arrive in America?

When Will Tsunami Debris Arrive in America?

On 11 March 2011, a devastating earthquake (Magnitude 9.0) and resultant tsunami struck northern Japan. The region suffering the greatest tsunami damage extended along the east coast from Chiba prefecture in the south (~35˚ N) to Iwate prefecture in the north (~40˚ N). News coverage of this event showed countless tons of debris washed to sea. Much of this will settle on the sea floor (e.g., automobiles) or biodegrade (e.g., paper products), but this debris will also include large quantities of floating plastics that will persist for decades.

Over the next five years, according to the Ocean Surface-Current Simulator (OSCURS), the debris will be broadly distributed by the North Pacific Subarctic and Subtropical Gyres along the West Coast of North America and into Garbage Patches. The west coast of North America can expect plastics from the tsunami on the beaches in the spring of 2013, with the highest concentrations in Oregon, Washington, and British Columbia. Around the summer of 2014, debris will be seen in Hawaii and in the NW Hawaiian Islands, with the highest concentrations likely at French Frigate Shoals.

Shown here is the estimated location of the debris as of May 31, 2011. Windage, i.e., the direct exposure of flotsam to wind drag, varies greatly. From experience with cargo container spills of tub toys, sneakers, hockey gloves and computer monitors, the wind factor employed in OSCURS varies between 1.0 for low windage objects like water slabs, to 2.0 for high windage objects like small derelict vessels.